Q6 / 100 · BITSAT 2024 (Memory Based Paper 1) · Chemistry

A stream of electrons from a heated filament was passed between two charged plates kept at a potential difference $V$ volt. If 'e' and $m$ are charge and mass of an electron, respectively, then the value of $h / \lambda$ (where $\lambda$ is wavelength associated with electron wave) is given by:

  • A
    $\sqrt{m \mathrm{e} V}$
  • Correct answer
    B
    $\sqrt{2 m \mathrm{e} V}$
  • C
    $m \mathrm{eV}$
  • D
    $2 m \mathrm{e} V$

Solution

As electron of charge ' $e$ ' is passed through ' $V$ ' volt, kinetic energy of electron will be eV . Wavelength of electron wave $(\lambda)=\frac{h}{\sqrt{2 m \cdot \mathrm{KE}}}$ $\lambda=-\frac{h}{\sqrt{2 m \mathrm{eV}}} \quad \therefore \frac{h}{\lambda}=\sqrt{2 m \mathrm{eV}}$

Hence, the correct answer is option: 'B'.

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